Monday, 13 October 2014

Health check reveals how glacier is declining due to warming climate... by Lauren Noakes

Researchers from the British Geological Survey have taken the very first comprehensive health check of a rapidly melting glacier. Their latest study reveals that their icy patient, the Falljökull glacier in south east Iceland, has been dramatically declining as it tries to adjust to recent changes in the climate.

The new findings on Falljökull show unhealthy changes in the glaciers behaviour and structure. Normal glacial patterns (growing in the winter and retreating in the summer) have been replaced by all year-round melting and rapid retreat of the margin of this Icelandic glacier, whilst its upper reaches continue to move forward. In fact the retreat has increased so dramatically over the last five years that there has been complete detachment of the stagnant lower section, like a lizard losing its tail. The team have published further information regarding this 'downsizing' behaviour on the BGS website.

“Over the past two decades due to the increasingly warmer summers and milder winters Iceland’s glaciers have been retreating at a dramatically accelerated rate.” commented Jez Everest, a glacial geologist at the BGS and co-author of the new paper.

The research could help scientists understand how other glaciers around the world, exhibiting similar early warning signs, could behave in the future. Working out how glaciers respond to changing climate is vitally important in a world where millions of people rely on them for drinking water and hydroelectric power.

Emrys Phillips, BGS research scientist and lead-author of the paper said, “We took a fully 3D view deep inside Falljökull and what we saw was rapid changes in the structure, a form of ‘downsizing’, to adjust to the changes in climate. We think that other steep, mountain glaciers around the world may be responding in a similar way, rapidly adjusting their active length in response to recent warming of the climate.” He also added “This type of behaviour has never been described before.”

Previously retreating glaciers are thought to behave in one of two ways: ‘active retreat’ where its margin oscillates backwards and forwards each year, retreating during the summer due to melting and moving forward in the cold winter months; and ‘passive retreat’ were it no longer moves but simply melts away like a giant ice cube (stagnates). Strangely, Falljökull does not fit neatly into either of these ‘pigeon holes’.

Using cutting-edge technologies BGS scientists were able to look inside the glacier. The monitoring techniques used by the team include:
• Ground Penetrating Radar to image inside the glacier and map the ice’s internal structure
• Terrestrial Laser scanning (LiDAR) to create a detailed 3D model of the surface of the glacier and surrounding glacial landforms
• four Global Navigation Satellite System (GNSS) stations installed onto the surface of the glacier to record its velocity
• digital mapping and measuring of the glaciers surface structures (fractures, crevasses, faults)

Using these techniques, the new study shows that between 1990 and 2004 the margin of Falljökull was ‘active’ with its seasonal oscillations leaving behind a series of ridge-like mounds of sediment which were pushed-up by the glacier during the winter months. But in 2004-2006 the margin of the glacier stopped moving altogether and began to melt back at an increasing rate.

However, time lapse photography and the GNSS/ GPS stations on the glacier surface clearly show that ice is still descending the icefall, and that the upper part of Falljökull is still flowing forward at between 50 and 70 meters per year.

The researchers have traced a large thrust fault cutting straight across the glacier just below a marked bulge in the glacier surface. This thrust is allowing the still ‘active’ upper part of the glacier to be pushed (thrust) over the lower reaches which stopped moving in 2004-2006.